CHEMISTRY CATALYSTS Spring 2014 – Week 12 (Kinetics/Gas Laws)

2 Boyle’s Law Boyle’s Law states that the pressure of a gas is inversely related to its volume when T and n are constant. if volume decreases, the pressure increases.

3 Freon-12, CCl 2 F 2, is used in refrigeration systems. What is the new volume in liters of an 8.0 L sample of Freon gas initially at 550 mm Hg after its pressure is changed to 2200 mm Hg while at constant T? 1. Set up a data table: Conditions 1Conditions 2 P 1 = 550 mm HgP 2 = 2200 mm Hg V 1 = 8.0 LV 2 = ???? Calculation with Boyle’s Law

4 Calculation with Boyle’s Law (Continued)

5 Learning Check For a cylinder containing helium gas indicate if cylinder A or cylinder B represents the new volume for the following changes (n and T are constant). 1) pressure decreases 2) pressure increases

6 Learning Check For a cylinder containing helium gas indicate if cylinder A or cylinder B represents the new volume for the following changes (n and T are constant). 1) pressure decreases B 2) pressure increases A

7 Learning Check

8 A sample of helium gas in a balloon has a volume of 6.4 L at a pressure of 0.70 atm. At 1.40 atm, is the new volume represented by A, B, or C?

9 Solution A sample of helium gas in a balloon has a volume of 6.4 L at a pressure of 0.70 atm. At a higher pressure, the new volume is represented by the smaller balloon A.

10 Learning Check A sample of oxygen gas has a volume of 12.0 L at 600. mm Hg. What is the new pressure when the volume changes to 36.0 L? (T and n constant).

11 Solution

Catalyst (5 minutes)  4/1/14 Gases  EQ: How do I use Charles’ Law?  A 450mL balloon filled with helium gas has a pressure of 770 mmHg. When the pressure increases to 900 mm Hg, what happens to the volume of the gas? Show your work.  If the pressure of a container increases by a factor of 3, predict what will happen to its volume.

Temperature Conversions  Convert 25°C to Kelvins. 25°C = 298 K  Convert 107°C to Kelvins. 107°C = 380 K  Convert 500 K to °C. 500K – 273 = 227 K  Convert 100 K to °C. 100 K – 273 = -173 °C

Charles’ Law In Charles’ Law, the Kelvin temperature of a gas is directly related to the volume. P and n are constant. when the temperature of a gas increases, its volume increases. 14

Charles’ Law: V and T 15 For two conditions, Charles’ Law is written (pressure and number of moles are constant)

Calculations Using Charles’ Law 16 A balloon has a volume of 785 mL at 21°C. If the temperature drops to 0°C, what is the new volume of the balloon (P constant)? 1. Set up data table: Conditions 1 Conditions 2 V 1 = 785 mLV 2 = ? T 1 = 21°C = 294 KT 2 = 0°C = 273K Be sure to use the Kelvin (K) temperature in calculations.

Calculations Using Charles’ Law (continued) 17

Learning Check 18 V 1 = 420 mL T 1 = 18ºC = 291K V 2 = 640 mL T 2 = ?

Catalyst (5 minutes)  4/3/14 Gases  EQ: How do I use Charles’ Law?  A 450mL balloon filled with helium gas has a temperature of 30˚C. When the temperature increases to 70˚C, what happens to the volume of the gas? Show your work.  If the volume of a container increases by a factor of 3, predict what will happen to its temperature.

Catalyst Review V 1 = 450 mL T 1 = 30ºC = 303K V 2 = ? mL T 2 = 70ºC = 343K

Gay-Lussac’s Law: P and T

A gas has a pressure at 2.0 atm at 18°C. What is the new pressure when the temperature is 62°C? (V and n constant) 1. Set up a data table. Conditions 1Conditions 2 P 1 = 2.0 atmP 2 = ??? T 1 = 18°C =291K T 2 = 62°C = 335K Calculation with Gay-Lussac’s Law

Try it

Dalton’s Law

The partial pressure of a gas  is the pressure of each gas in a mixture.  is the pressure that gas would exert if it were by itself in the container. Partial Pressure

Dalton’s Law of Partial Pressures indicates that  pressure depends on the total number of gas particles, not on the types of particles.  the total pressure exerted by gases in a mixture is the sum of the partial pressures of those gases. P T = P 1 + P 2 + P Dalton’s Law of Partial Pressures

For example, at STP, one mole of a pure gas in a volume of 22.4 L will exert the same pressure as one mole of a gas mixture in 22.4 L. V = 22.4 L Gas mixtures Total Pressure 0.5 mole O mole He 0.2 mole Ar 1.0 mole 1.0 mole N mole O mole He 1.0 mole 1.0 atm